I did try around the time it split from the normal releases (6.0?). The overall feeling I got was that lots of simple things don't work, trivial bugs stay open for... well mine are still open and there was next to no documentation for any kind of troubleshooting. NDB returned error numbers which were not properly translated by mysql_error, so you were left looking them up the hard way. There was also next to no community - just one IRC channel where guru ndb hackers seemed to know everything about it... but any kind of debugging through them was pretty hard if you ended up with a "I've got a XXGB db which just doesn't come up, what do I do?" situation.

If this has improved lately, I'd be very interested to hear about the changes!